It was 50 years ago this week. On Feb. 9, 1964, four mop-topped British working-class lads in matching mod suits and speaking in exotic Liverpudlian accents took a TV studio stage in New York City to the deafening shrieks of teenage girls. And the world changed.

This Sunday marks a half-century since The Beatles made their inaugural appearance on “The Ed Sullivan Show.” Broadcast in primitive black and white, the program was viewed by a then-record audience of 73 million people, some 45 percent of American households with TV sets. In those pre-cable, pre-YouTube, pre-Twitter days, when family members actually talked and bickered with one another in living rooms in front of boxy TVs equipped with rabbit-ear antennas, John, Paul, George and Ringo went viral.

I was a toddler then. But I still remember my older sister screaming and dancing and kissing the TV. Even my opera-buff parents didn’t mind. For The Beatles were more than pleasant faces in skinny pants. They wrote and performed their own music, with John Lennon and George Harrison on guitar, Paul McCartney on bass guitar, and Ringo Starr (real name Richard Starkey) on drums. They were endearingly goofy.

Shortly after the band arrived on this side of the Atlantic, John was asked by a reporter, “How do you find America?’’

“Turned left at Greenland,’’ he said in a bit captured in the 1964 movie “A Hard Day’s Night.’’

The Beatles had already conquered western Europe. But Paul wasn’t sure of the band’s future in the United States. “They’ve got their own groups,” he was quoted as saying before the band’s first US tour. “What are we going to give them that they don’t already have?”

But people of this country, traumatized by President John F. Kennedy’s assassination 79 days earlier and wrenched by the escalating Vietnam War, looked for distractions. The peppy guys from Liverpool, England, fit the bill. As my family bopped to the music, we had no idea The Beatles would become the most influential band, well, ever.

As if it weren’t enough that The Beatles ignited the British Invasion of American popular music, the Fab Four put their mark on every facet of the culture, from fashion and hairstyles to the way Americans thought about youth and superstardom.

In coming years, The Beatles would grow, with complex tunes on “Rubber Soul,” “Revolver” and “Sgt. Pepper’s Lonely Hearts Club Band.”

And was “Lucy in the Sky with Diamonds,” the 1967 hit from “Sgt. Pepper’s,” a cheeky reference to LSD? Paul confirmed it was in 2004. But John, who admitted to using the mind-altering drug, maintained that it was mere coincidence that the first letters of the tune’s title nouns spelled out LSD. The song, he said, was named for a drawing called “Lucy — in the sky with diamonds’’ by his then-4-year-old son, Julian.

Nat Meguid, 14, of Connecticut wasn’t even a thought when The Beatles first appeared on television. Now she’s a Beatlemaniac, who listens to the band every day on her iPod or vinyl records, which sound infinitely better.

“The Beatles cover all my emotions,” she told me. “I feel like I can just tune out and all my problems disappear. Nobody else comes close to The Beatles. Sometimes I think I was born too late.’’

As George’s song tells us, all things must pass.

In 1970, Paul announced that, 10 years after the band’s formation (Ringo replaced drummer Pete Best in 1962; the late bass player Stuart Sutcliffe left the then-five-piece act in ’61), The Beatles were finished. Though John’s second wife, Yoko Ono, is blamed by many fans for breaking up the band, pulling John from the group and causing friction among bandmates, the fact is that the lads could no longer stand each other.

In 1980, John Lennon was shot dead outside his apartment at The Dakota on Manhattan’s Central Park West by Mark David Chapman. John was 40. In 2001, George Harrison died of lung cancer at 58.

Then last month at the Grammy Awards ceremony in Los Angeles, Paul McCartney, now 71 — or Sir Paul since he was knighted by Queen Elizabeth in 1997 — won a trophy for Best Rock Song for his tune “Cut Me Some Slack.” Then he topped himself by rocking out with a little help from his friend Ringo Starr, 73. Taking the stage together they performed Paul’s song “Queenie Eye” with Paul on piano and Ringo on drums. The assembled stars gave the surviving Beatles a standing ovation. Watching from home, I had tears in my eyes.

Fifty years from now, another generation will revere The Beatles. Rock on.

Follow his bro to hell

Three innocents died, including an 8-year-old boy, and 264 were injured. Sixteen people lost all or part of a limb. Three lost more than one. These people were not at war, they were runners and spectators at last year’s Boston Marathon.

Federal prosecutors say they’ll seek the death penalty for Dzhokhar Tsarnaev, now 20, charged with using a weapon of mass destruction, and other crimes, by setting off two pressure-cooker bombs near the race’s finish line. Tsarnaev’s brother, Tamerlan, 26, escaped justice after trying to flee. He was shot by police, then run down and dragged by a stolen Mercedes SUV driven by his own brother.

An ethnic Chechen from Russia, Dzhokhar Tsarnaev was a naturalized American citizen. He sought revenge against US troops for attacking Muslims, he reportedly wrote with marker inside the boat in which he hid before his capture. To this fiend, marathon victims were “collateral damage.’’

Inflicting the ultimate penalty is the only way to end this madness.

School of hard Knox

Amanda Knox is an American accused in Italy of stabbing to death her British college flatmate in a 2007 sex game. But after Knox and her Italian ex-beau Raffaele Sollecito were convicted and sentenced to 26 years apiece in prison, an Italian appeals court in 2011 said forget about it — and reversed the decision. Knox returned home to Seattle.

Italy wasn’t done with her.

Last week, the allegedly homicidal duo was again convicted. Knox, now 26, was in the United States at the time, and vows never to return to Italy to serve her new, 28¹/₂-year sentence. (Sollecito got 25 years.) I don’t know if author Nina Burleigh is correct in concluding that the woman dubbed “Foxy Knoxy’’ by the media was nailed because of her beauty. Under American law, Knox could not be tried twice for the same crime.

Think about that before studying abroad. . .

Talk about a meal ticket!

A freeloading foodie bought a first-class, fully refundable ticket from China Eastern Airlines, but he never flew. He booked, then canceled, 300 flights in a year, each time dining free of charge in an airport VIP lounge, the Malaysian newspaper Kwong Wah Yit Poh reported. The free grub ended after the man was confronted by airline officials.

Instead, the man took a full refund on his ticket. All this to score free airline food. Sad.

A class-less move by de Blasio

It’s a bonehead move. Mayor de Blasio plans to snatch $210 million that former Mayor Bloomberg intended to be used to expand charter schools, and use the cash to pay for 2,100 pre-kindergarten seats.

Charters, many in poor neighborhoods, tend to outperform standard schools. While they’re publicly funded, they’re privately managed, and teachers are usually not union members. That means incompetents can easily be fired.